1. Field of the Invention
The present invention relates to a method of transferring a plate-like substrate, e.g., a semiconductor wafer, between a substrate holding member and a substrate support member.
2. Description of the Related Art
For example, a semiconductor manufacturing process includes a step of subjecting a substrate to a heat treatment, e.g., a semiconductor wafer, and a heat treatment apparatus for performing batch heat treatment of a large number of substrates is recently used to achieve required heat treatment efficiently. In a heat treatment apparatus of this type, when a large number of substrates transferred from a substrate holding member, e.g., a carrier, are supported by an arbitrary substrate support member, the substrate support member is loaded in a reaction vessel. After predetermined heat treatment is performed, the substrate support member is directly removed from the reaction vessel. As the substrate support member, a wafer boat made of quartz is usually used.
Semiconductor wafers are transferred to the wafer boat by a transfer unit. The operation of the transfer unit is controlled by a control mechanism in accordance with a predetermined pattern. The operation of the transfer unit must be accurately performed for an actually installed wafer boat.
The wafer boat must be periodically cleaned as reaction products and the like attach to contaminate it during a heat treatment step and the like. It is, however, almost impossible to install a cleaned wafer boat in a state strictly the same as that of the wafer boat before cleaning. More specifically, it is very difficult to completely restore the installation position or posture of the wafer boat after the wafer boat is cleaned. A deformation or distortion is sometimes caused in the wafer boat due to cleaning and heating at a temperature of 1,000.degree. C. or more. Furthermore, wafer boat replacement is sometimes performed. In such a case, when the transfer unit is operated in accordance with the same operation pattern as that employed before cleaning or replacement, the semiconductor wafer cannot be appropriately supported by the wafer boat, and is incompletely supported by the wafer boat. Then, the semiconductor wafer may drop, or sometimes the wafer boat may be knocked down by a semiconductor wafer which is to be supported to the wafer boat by the transfer unit.
From these situations, when a new wafer boat is installed, the operation pattern of the transfer unit must be adjusted (subjected to teaching) so that a transfer operation matching to the wafer boat is executed.
Conventionally, teaching of the transfer unit is manually performed. More specifically, when the forks of the transfer unit are inserted in the wafer boat, the operator finely adjusts the forks by visually confirming adjustment state of the vertical movement, swing movement, and forward-and-backward movement of the forks such that the positions of the forks and the support grooves of the wafer boat relative to each other become appropriate, thereby performing this teaching in accordance with visual confirmation in a trial-and-error manner.
However, since this teaching is performed by confirmation and adjustment of the positions of the forks of the transfer unit with respect to all the support grooves of the wafer boat, this requires a very large operation load and a long operation time, while it cannot always obtain high reliability.